The present invention relates to the field of use of optical fibers for non-destructive evaluation (NDE) of polymer matrix composite structural members. More particularly, the present invention is a method for detecting flaws in structural members made of polymer matrix composite materials by utilizing optical fibers in the structural composites themselves.
Various polymer resin matrix composite materials are well known in the art. Glass fibers are the most common of all reinforcing fibers for polymer matrix composites. For structural composites, the two commonly used glass fibers are E-glass and S-glass. These glass fibers are primarily composed of a silica (SiO2) backbone in the form of a SiO4 tetrahedra. The silicas are then doped with modifier ions that can contribute to their glass properties and manufacturing capability. However, fiberglass composites have not been able, as of yet, to prove their durability and serviceability. Fiberglass composites need to become more predictable, like steel, in order to be used extensively with a high degree of confidence in their structural integrity. Therefore, there is a need for a method for detecting flaws in the composite polymer matrix structural members.
A primary objective of the present invention is the provision of a method of detecting flaws in structural members.
Another objective of the present invention is the provision of a method of detecting flaws in structural members that involves the integration of optical fibers into the composite matrix to the substantial exclusion of traditional glass fibers.
Another objective of the present invention is to more easily permit non-destructive evaluation of structural members.
Another objective of the present invention is the provision of a method of detecting flaws in structural members that permits an onlooker or investigator to easily evaluate the integrity of the entire composite structural member.
Another objective of the present invention is the provision of a method of detecting flaws in structural members that is reliable and inexpensive to use.
These and other objectives will become apparent to one skilled in the art in view of the drawings, as well as the description and claims that follow.
The present invention relates to a method for detecting flaws in structural members made of polymer matrix composite materials by utilizing optic fibers and preferably only optic fibers, in the structural composites. The method includes taking a quantity of polymer matrix material that is substantially free of any non-optic glass fibers, molding the matrix material into a structural loadbearing member having a length and opposite ends surfaces, placing a plurality of continuous individual straight elongated fiber optic strands having the same length as the loadbearing member in the matrix material before molding, loading the structural member to exert stress and strain thereon, exposing one of the ends of the fiber optic strands to a source of light, viewing the opposite ends of the fiber optic strands to determine if light is being emitted therefrom by passing through the fiber optic strands, and making an evaluation of any structural flaws in the member by determining whether light from the light source has been fully transmitted through the fiber optic strands.